The present invention is generally directed to motor housings, and more specifically is directed to a pump motor housing having an improved cooling means for cooling the motor.
The present invention finds particular utility in the areas of water and wastewater treatment and may be considered most effective when used in association with centrifugal pumps. Large motors which drive centrifugal pumps require effective cooling to prevent overheating of their electrical components. Many cooling systems for motors and pump motors are known in the art. Some pump motors use the liquid which is being pumped as the motor coolant and circulate it inside the motor housing in contact with the motor assembly components. This type of construction presents certain problems. Care must be taken to effectively insulate the motor electrical components from contact with solids or pollutants in the pumped liquid contained within the motor chamber.
Other pump motor constructions require great expense through complex machining to the exterior housing of the motor and fitting with a coolant jacket. Still other pump motor constructions submerge the motor assembly components in oil in the motor housing. When submerged in oil, the motor rotor will experience increased drag during operation resulting in friction losses. These friction losses affect the efficiency ratio of the pump motor of rated horsepower to output horsepower. Additionally, the cooling oil has to be monitored because of its likelihood of breaking down due to frictional heating, thereby leading to increased maintenance,
The present invention concerns itself with providing cooling to a pump motor wherein the pump motor assembly operates in air, rather than in oil.
Some attempts have been made in the art to provide cooling to air-filled pump motors. One such attempt is described in U.S. Pat. No. 2,784,672, issued Mar. 12, 1957, which describes a pump and motor assembly having an annular cooling channel formed in a double wall motor housing. The liquid being pumped is circulated through this cooling channel to provide cooling for the pump motor. Because the pump impeller is used to pump the pumped liquid and it through the annular cooling cavity of the motor housing, it increases the draw on the output horsepower of the motor.
Another attempt is described in U.S. Pat. No. 5,250,863, issued Oct. 5, 1993 in which the pump motor housing has a separate exterior cooling jacket positioned over it, offset from its centerline to provide an annular passage of varying thickness for circulation of cooling fluid. This cooling jacket is an additional component and thereby adds to the cost and complexity of the pump. This pump also uses the pump impeller to circulate the coolant through the cooling jacket, which reduces the overall efficiency of the pump.
The present invention is directed to a pump motor housing construction which overcomes the aforementioned disadvantages and provides improved cooling to the pump motor without a substantial reduction of the efficiency of the pump motor.
Accordingly, it is a general object of the present invention to provide a pump motor housing for an air-filled motor assembly with improved heat transfer characteristics.
It is another object of the present invention to provide a centrifugal pump driven by an electric motor which is disposed within a motor housing having a closed loop cooling circuit comprising a plurality of coolant passages extending along the length of the motor housing, the coolant passages being in communication with different fluid pressure regions of a coolant reservoir disposed within the motor housing which fluid pressure differential assists in the circulation of coolant through the cooling circuit.
It is a further object of the present invention to provide a motor housing having an improved cooling means and suitable for use in association with a motor driving a centrifugal pump in which the housing has a plurality of coolant passageways extending along the motor housing, some of the passageways being in communication with a high pressure region of the motor housing and other of the passageways being in communication with a low pressure region of the motor housing, whereby fluid pressure developed during operation of the motor assists in circulating the coolant through the cooling circuit and wherein a coolant reservoir has a heat transfer surface in contact with the liquid being pumped.
It is yet still another object of the present invention to provide a motor housing for a pump motor intended for use on dry-pit centrifugal pumps in which the motor housing has a plurality of cooling passages integrally formed in the housing sidewalls, the cooling passages having a plurality of lift passages with entrance ports communicating with the high pressure area of a reservoir disposed within the housing and the cooling system further including a plurality of coolant return passages with exit ports communicating with the low pressure area of the fluid reservoir, whereby the cooling may be effectively circulated through the cooling circuit by way of a secondary impeller disposed in the motor housing on a motor shaft, the secondary impeller creating the high pressure area at the outermost portions of the reservoir.
Yet another object of the present invention is to provide a pump motor housing within improved cooling characteristics intended for use with in-air motors in which the motor is submerged within the motor housing in a cooling fluid and in which the motor housing incorporates a closed loop cooling fluid pathway, the cooling fluid being driven in circulation through the fluid pathway by means of a vortex impeller disposed on the motor shaft within the housing, the vortex impeller creating, during rotation of the motor thereof, define regions of high and low pressure within an internal fluid reservoir, the cooling fluid entry pathways communicating with the high pressure areas and the cooling fluid return pathways communicating with the low fluid pressure areas to promote efficient circulation of cooling fluid throughout the interior of the pump motor housing.
These and other objects, features and advantages of the present invention will be clearly understood through consideration of the following detailed description.